Slab allocators: Drop support for destructors

There is no user of destructors left.  There is no reason why we should keep
checking for destructors calls in the slab allocators.

The RFC for this patch was discussed at
http://marc.info/?l=linux-kernel&m=117882364330705&w=2

Destructors were mainly used for list management which required them to take a
spinlock.  Taking a spinlock in a destructor is a bit risky since the slab
allocators may run the destructors anytime they decide a slab is no longer
needed.

Patch drops destructor support.  Any attempt to use a destructor will BUG().

Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Acked-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 0 insertions, 5 deletions

diff --git a/mm/slob.c b/mm/slob.c
index 57bb72ed0d4..79164a4f54a 100644
--- a/mm/slob.c
+++ b/mm/slob.c
@@ -280,7 +280,6 @@ struct kmem_cache {
         unsigned long flags;
         const char *name;
         void (*ctor)(void *, struct kmem_cache *, unsigned long);
-        void (*dtor)(void *, struct kmem_cache *, unsigned long);
 };
 
 struct kmem_cache *kmem_cache_create(const char *name, size_t size,
@@ -296,13 +295,11 @@ struct kmem_cache *kmem_cache_create(const char *name, size_t size,
                 c->name = name;
                 c->size = size;
                 if (flags & SLAB_DESTROY_BY_RCU) {
-                        BUG_ON(dtor);
                         /* leave room for rcu footer at the end of object */
                         c->size += sizeof(struct slob_rcu);
                 }
                 c->flags = flags;
                 c->ctor = ctor;
-                c->dtor = dtor;
                 /* ignore alignment unless it's forced */
                 c->align = (flags & SLAB_HWCACHE_ALIGN) ? SLOB_ALIGN : 0;
                 if (c->align < align)
@@ -371,8 +368,6 @@ void kmem_cache_free(struct kmem_cache *c, void *b)
                 slob_rcu->size = c->size;
                 call_rcu(&slob_rcu->head, kmem_rcu_free);
         } else {
-                if (c->dtor)
-                        c->dtor(b, c, 0);
                 __kmem_cache_free(b, c->size);
         }
 }